Chemistry Worksheet
Name: ______________________________
More Nomenclature (polyatomic ions & acids)
Block: ______ Date: __________________
1. Naming and Formula Writing for Ionic Compounds Containing Polyatomic Ions: Polyatomic ions are ions that consist of many atoms with an overall charge. For example, the polyatomic ion hydroxide consists of an oxygen bound to a hydrogen with an overall negative charge. The formula for hydroxide is OH-. Another example, sulfate (SO42−), consists of four oxygens bound to a sulfur with an overall charge of 2−. Naming and formula writing for compounds containing polyatomic ions is very similar to that of binary ionic compounds. The notable difference is polyatomic ions require parentheses if more than one polyatomic ion is depicted in the formula. For example, the formula for strontium hydroxide is Sr(OH) 2, not SrOH2. On the other hand, the formula for sodium hydroxide is written NaOH, and not Na(OH). No parentheses are required around the hydroxide in the formula for sodium hydroxide because only one hydroxide is present in one formula unit of sodium hydroxide.
Compound
Name
a. CaSO4
___________________________________________
b. Pb(OH)2
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c. K2SO4
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d. Mg(NO3)2
___________________________________________
e. CuSO4
___________________________________________
f. Na3PO4
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g. SnO2
___________________________________________
h. (NH4)2SO4
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2. Write the formulas for the following compounds containing polyatomic ions. Be aware that most polyatomic ions are anions. A notable exception is the cation ammonium. Ammonium has the formula NH4+.
Compound
Formula
a. tin(II) sulfate
___________________________
b. calcium nitrate
___________________________
c. ammonium carbonate
___________________________
d. lead(II) sulfate
___________________________
e. ammonium hydroxide
___________________________
f. barium hydroxide
___________________________
g. aluminum phosphate
___________________________
h. tin(IV) phosphate
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3. Naming and Formula Writing for Acids A substance that releases H+ when dissolved in water is an acid. Acids generally can be recognized because the first element in the formula is hydrogen. For example, HCl(aq) is an acid. Your book provides rules for writing the names of acids. Acids are named after the anion in the formula. For binary acids, add the prefix hydro– and the suffix –ic to the root of the anion name. The above binary acid, HCl, is thus hydrochloric acid. Acids containing polyatomic ions can be named by simply changing the ending of the anion. The ending –ate is changed to –ic, and the ending –ite is changed to –ous. For example, HNO3(aq) contains the anion nitrate, and is thus named nitric acid. HNO2(aq) contains the anion nitrite, and is thus named nitrous acid. Note than no hydro- prefix is used for naming acids with polyatomic ions. The following pneumonic device can be used to remember the rules for naming acids containing polyatomic ions. “I took a b(-ite), and it made me nausea(-ous). I (-ate) it, and it made me s(-ic)k.”
Acid
Name
a. HF(aq)
___________________________________________
b. HNO3(aq)
___________________________________________
c. H2SO3(aq)
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d. HBr(aq)
___________________________________________
e. H2SO4(aq)
___________________________________________
f. H3PO4(aq)
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g. HCcH3O2(aq)
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4. Write the formulas for the following acids. Be aware that most polyatomic ions are anions. A notable exception is the cation ammonium. Ammonium has the formula NH4+.
Acid
Formula
a. hydrochloric acid
___________________________
b. phosphoric acid
___________________________
c. hydrosulfuric acid
___________________________
d. carbonic acid
___________________________
e. chlorous acid
___________________________
f. nitrous acid
___________________________
g. hydroiodic acid
___________________________
h. acetic acid
___________________________
Chemistry Worksheet
Name: ______________________________
More Nomenclature (polyatomic ions & acids) 5. Answer the following review questions.
Block: ______ Date: __________________
a. What is a polyatomic ion?
b. Use examples to illustrate why parentheses are sometimes needed in writing the formulas for ionic compounds containing polyatomic ions.
c. How can you recognize an ion is polyatomic by looking at the name?
d. What are notable exceptions to your answer to number 3?
e. What ending is used for all anions in the formulas for binary compounds? (Think back to your 1st nomenclature worksheet).
f. Most polyatomic ions are anions. What is a notable exception, and what is its formula?
g. What is an acid? Why is the state of matter (aq) frequently written after the formula for an acid?
h. Why is only the anion, and not the cation, considered in naming acids?
